Luciano Galano

Seismic Behavior of Short Coupling Beams with Different Reinforcement Layouts

This paper presents an experimental investigation on the seismic behavior of reinforced concrete coupling beams. The reinforcement layout and the loading history were the main variables of the tests. Fifteen short coupling beams with four different reinforcement arrangements were tested. They were subjected to monotonic and cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 0.75. The reinforcement layouts consisted of a classical scheme, diagonal scheme without confining ties, diagonal scheme with confining ties, and inclined bars to form a rhombic configuration. Concrete compressive strengths of the specimens varied from 40 MPa to 54 MPa. Test results showed that the beams with diagonal or rhombic reinforcement layouts behaved better than beams with longitudinal arrangement of the steel bars. These results were produced by the different resisting truss mechanisms that were developed in the coupling beams after the first cracking. The differences in energy dissipation were negligible between the diagonal and rhombic layouts. The rhombic arrangement, however, was more advantageous in terms of rotational ductility capacity and decay in strength and stiffness of the beams. Moreover, cyclic tests demonstrated that the behavior of the rhombic layout was less affected by the different loading histories.

Strength and Ductility of HSC and SCC Slender Columns Subjected to Short-Term Eccentric Load

Although several methods to predict the ultimate strength of slender columns under eccentric loads are available, the reliability of these approaches has been extensively investigated only for columns made of conventional concrete. This paper seeks to expand available experimental data for slender columns of high strength concrete (HSC) and self-consolidating concrete (SCC). Tests were conducted on 60 eccentrically-loaded slender columns constructed of HSC, SCC, and traditional vibrated concrete. All columns have cross sections of 100 x 100 mm (3.94 x 3.94 in.) and lengths of 2000 mm (78.8 in.). The main variables considered in the tests were the concrete strength, the longitudinal steel reinforcement ratio, and the load eccentricity. Attention is focused on the overall performance of columns: type of failure, cracking pattern, peak strength, and ductility. Findings from the tests carried out with small eccentricity indicate that the ultimate normalized strengths of SCC slender columns are lower than the strengths obtained for the traditional vibrated concrete columns. The tests carried out with medium and high eccentricities showed comparable strengths. The tests on SCC columns made of normal-strength concrete showed very soft and ductile failures. In these columns, cracking patterns are located along the whole length of the specimens with a high number of cracks. More concentrated damage was observed in the medium-strength concrete and HSC columns. The ductility of slender columns was higher for the SCC columns made of normal-strength concrete. For medium-strength concrete and HSC, no notable differences were observed between SCC and vibrated columns.

In Situ Shear and Compression Tests in Ancient Stone Masonry Walls of Tuscany, Italy

The present paper reports methods and results of an extensive experimental project performed to assess the mechanical characteristics of ancient stone masonry walls of Tuscany (Italy). Some relevant considerations concerning the determination of common design shear strength parameters via experimental test results are also presented. Results from 22 in situ tests performed on nine large-scale stone masonry panels are reported. Test panels were selected as part of shear walls in six different old masonry buildings in the northern part of Tuscany so as to represent a reliable sample of the most common masonry types in this region. In situ tests were carried out according to experimental schemes for vertical compression, shear compression, and diagonal compression. After the first test, several panels were repaired and reinforced by means of cement mortar injections (full cement grouting) or reinforced concrete (RC) jackets, and then tested again to determine the effectiveness of the intervention. Particular attention was then devoted to evaluate the referential shear strength τk of these masonry assemblages in the original state. To this purpose, a fitting process for experimental data was used, adopting two different schemes for interpretation of the shear strength of masonry (the Coulomb and the Tumsek-Cacovic equations). The results from this work have shown that the Turnsek-Cacovic equation gives a better fit to experimental data than the Coulomb equation, especially for medium- and poor-quality masonry walls. Finally, conclusions are presented noting the difference between shear strength values calculated from fitting the data from test results and the values suggested by European and Italian standards.

Seismic Response Of Masonry Plane Walls: A Numerical Study On Spandrel Strength

The paper reports the results of a numerical investigation on masonry walls subjected to in‐plane seismic loads. This research aims to verify the formulae of shear and flexural strength of masonry spandrels which are given in the recent Italian Standards [1]. Seismic pushover analyses have been carried out using finite element models of unreinforced walls and strengthened walls introducing reinforced concrete (RC) beams at the floor levels. Two typologies of walls have been considered distinguished for the height to length ratio h/l of the spandrels: a) short beams (h/l = 1.33) and b) slender beams (h/l = 0.5). Results obtained for the unreinforced and the strengthened walls are compared with equations for shear and flexural strength provided in Standards [1]. The numerical analyses show that the reliability of these equations is at least questionable especially for the prediction of the flexural strength. In the cases in which the axial force has not been determined by the structural analysis, Standards ...

Finite Element Modelling for Seismic Assessment of Historic Masonry Buildings

The chapter discusses on the use of the finite element modelling technique for the seismic assessment of historic masonry buildings, outlining that advanced numerical analyses can provide significant information to understand their actual structural behaviour. A finite element methodology for the static and dynamic nonlinear analysis of historic masonry structures is described and exemplified through the discussion of two representative case studies: a masonry church and an old residential building.

Diagonal cracking shear strength of unreinforced masonry panels: a correction proposal of the b shape factor

Abstract After summarising the failure criteria adopted by the new Italian Seismic Code (NTC 2008) for the seismic assessment of unreinforced masonry panels (URM), the paper presents a numerical study aimed at investigating the b shape factor. This factor is a coefficient, function of the panels’ slenderness, employed to evaluate the ultimate shear strength of URM for the failure mechanism with diagonal cracking. The results herein presented show that the actual values of the coefficient b are higher than those proposed by the NTC (2008); consequently, the shear strength obtained by applying the Italian Seismic Code is not conservative. An amendment is proposed for the b shape factor, and its effects are evaluated through the analysis of three plane-URM walls with regular openings and different slenderness of the masonry beams. Pushover analyses were performed to estimate their seismic capacity and their collapse modes. The walls were modelled by both the finite element method (FEM) and the equivalent frame approach (EFM). In the EFM approach the b shape factor was selected both according to the NTC (2008) and as proposed in the paper. The seismic capacity curves show that the EFM approach significantly overestimate the ultimate shear strength of the walls with respect to the results obtained by the FEM, and this effect is amplified when the b shape factor is evaluated as recommended by the NTC (2008).

Performance Of Distributed Base Isolation System For Masonry Buildings

The paper presents results from a research study on a new distributed base isolation system for masonry buildings. This system consists of a layer of mortar interposed between the top face of foundations and the shear walls base. The mortar layer is reinforced with vertical mild steel bars. anchored both to masonry walls and to subside concrete of foundations. The proposed system is simple and inexpensive and it is capable of high degree of protection. To demonstrate its effectiveness, the seismic response of a masonry building is investigated by simplified 2 DOFs mathematical model performing numerical analyses in the time domain. Parameters involved in this study were: the fixed-base natural period of the building, the mass ratio. the isolation degree and, the ratio between the yield level of the soft base and the ultimate strength of the shear walls. Comparisons between dynamic responses of fixed-base and isolated models are presented in the form of spectral quantities. Results show that this type of isolation is capable of significantly reducing accelerations at the floor level, with performance comparable to FSI schemes. and a n additional advantage of reducing amplitude of residual displacements.

Critical Conditions: Yield Criteria

This chapter presents some classical yield criteria describing the phase transition from linear elasticity to other states such as plastic and cracked.

Euler’s Analysis of Critical Loads: Bifurcation Phenomena

This chapter is an introduction to bifurcation phenomena. Attention is focused primarily on the Euler rod.

Constitutive Structures: Basic Aspects

In this chapter, we explain the necessity of introducing what we commonly call constitutive structures and indicate in an isothermal setting a mechanical dissipation inequality as a source of a priori constitutive restrictions. We focus attention essentially on the elastic behavior, and when there are large strains, we show the physical incompatibility between objectivity of the elastic energy and the convexity of the energy itself with respect to the deformation gradient. Then we discuss the elastic behavior in the small-strain regime. We present the notions of material isomorphism and material symmetries, indicating how they allow us to distinguish between simple solids and fluids. Among material symmetries, we discuss isotropy at length. We then include some digressions on viscous materials, showing how the introduction of the incompressibility internal constraint in this case leads to the Navier–Stokes equations.